package com.knziha.plod.widgets;

import android.os.Build;

import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.X509TrustManager;

public class SSLSocketFactoryCompat extends SSLSocketFactory {
	private SSLSocketFactory defaultFactory;
	// Android 5.0+ (API level21) provides reasonable default settings
	// but it still allows SSLv3
	// https://developer.android.com/about/versions/android-5.0-changes.html#ssl
	static String protocols[] = null, cipherSuites[] = null;
	
	static {
		try {
			SSLSocket socket = (SSLSocket) SSLSocketFactory.getDefault().createSocket();
			if (socket != null) {
				/* set reasonable protocol versions */
				// - enable all supported protocols (enables TLSv1.1 and TLSv1.2 on Android <5.0)
				// - remove all SSL versions (especially SSLv3) because they're insecure now
				List<String> protocols = new LinkedList<>();
				for (String protocol : socket.getSupportedProtocols())
					if (!protocol.toUpperCase().contains("SSL"))
						protocols.add(protocol);
				SSLSocketFactoryCompat.protocols = protocols.toArray(new String[protocols.size()]);
				/* set up reasonable cipher suites */
				if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
					// choose known secure cipher suites
					List<String> allowedCiphers = Arrays.asList(
							// TLS 1.2
							"TLS_RSA_WITH_AES_256_GCM_SHA384",
							"TLS_RSA_WITH_AES_128_GCM_SHA256",
							"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
							"TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
							"TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
							"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
							"TLS_ECHDE_RSA_WITH_AES_128_GCM_SHA256",
							// maximum interoperability
							"TLS_RSA_WITH_3DES_EDE_CBC_SHA",
							"TLS_RSA_WITH_AES_128_CBC_SHA",
							// additionally
							"TLS_RSA_WITH_AES_256_CBC_SHA",
							"TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA",
							"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
							"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
							"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA");
					List<String> availableCiphers = Arrays.asList(socket.getSupportedCipherSuites());
					// take all allowed ciphers that are available and put them into preferredCiphers
					HashSet<String> preferredCiphers = new HashSet<>(allowedCiphers);
					preferredCiphers.retainAll(availableCiphers);
					/* For maximum security, preferredCiphers should *replace* enabled ciphers (thus disabling
					 * ciphers which are enabled by default, but have become unsecure), but I guess for
					 * the security level of DAVdroid and maximum compatibility, disabling of insecure
					 * ciphers should be a server-side task */
					// add preferred ciphers to enabled ciphers
					HashSet<String> enabledCiphers = preferredCiphers;
					enabledCiphers.addAll(new HashSet<>(Arrays.asList(socket.getEnabledCipherSuites())));
					SSLSocketFactoryCompat.cipherSuites = enabledCiphers.toArray(new String[enabledCiphers.size()]);
				}
			}
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}
	
	public SSLSocketFactoryCompat(X509TrustManager tm) {
		try {
			SSLContext sslContext = SSLContext.getInstance("TLS");
			sslContext.init(null, (tm != null) ? new X509TrustManager[]{tm} : null, null);
			defaultFactory = sslContext.getSocketFactory();
		} catch (GeneralSecurityException e) {
			throw new AssertionError(); // The system has no TLS. Just give up.
		}
	}
	
	private void upgradeTLS(SSLSocket ssl) {
		// Android 5.0+ (API level21) provides reasonable default settings
		// but it still allows SSLv3
		// https://developer.android.com/about/versions/android-5.0-changes.html#ssl
		if (protocols != null) {
			ssl.setEnabledProtocols(protocols);
		}
		if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP && cipherSuites != null) {
			ssl.setEnabledCipherSuites(cipherSuites);
		}
	}
	
	@Override
	public String[] getDefaultCipherSuites() {
		return cipherSuites;
	}
	
	@Override
	public String[] getSupportedCipherSuites() {
		return cipherSuites;
	}
	
	@Override
	public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
		Socket ssl = defaultFactory.createSocket(s, host, port, autoClose);
		if (ssl instanceof SSLSocket)
			upgradeTLS((SSLSocket) ssl);
		return ssl;
	}
	
	@Override
	public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
		Socket ssl = defaultFactory.createSocket(host, port);
		if (ssl instanceof SSLSocket)
			upgradeTLS((SSLSocket) ssl);
		return ssl;
	}
	
	@Override
	public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
		Socket ssl = defaultFactory.createSocket(host, port, localHost, localPort);
		if (ssl instanceof SSLSocket)
			upgradeTLS((SSLSocket) ssl);
		return ssl;
	}
	
	@Override
	public Socket createSocket(InetAddress host, int port) throws IOException {
		Socket ssl = defaultFactory.createSocket(host, port);
		if (ssl instanceof SSLSocket)
			upgradeTLS((SSLSocket) ssl);
		return ssl;
	}
	
	@Override
	public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
		Socket ssl = defaultFactory.createSocket(address, port, localAddress, localPort);
		if (ssl instanceof SSLSocket)
			upgradeTLS((SSLSocket) ssl);
		return ssl;
	}
}